A number of different compositions and methods for disinfecting flush toilets have been proposed. These include various hypochlorite and chloramine compounds, that can be dispensed from a single-compartment dispenser, such as is described in U.S. Pat. No. 4,318,891, or from a two-compartment dispenser such as is described in U.S. Pat. No. 3,618,143 or 4,208,746. The disinfecting composition can be employed as granules, but is more commonly employed as a tablet.
In order to act effectively in automatic toilet bowl cleaners, the disinfectant tablet must have a number of properties. The tablet should have a useful life approaching 300 flushes, and should produce a disinfectant concentration from about 2 to about 30 parts per million, preferably from about 5 to about 120 parts per million, per flush. The tablet must not produce objectionable chloramine or other objectionable odors. The tablets must retain their integrity through the useful life of the toilet bowl cleaner and must not crumble or disintegrate so as to plug the various holes and passages in the dispenser, through which water is circulated as the toilet tank fills and drains. The disinfectant tablet must not cause corrosion of the metal parts of the toilet or other adverse effects on other portions of the fixtures. The tablet must not appreciably contribute to formation of scale or other insolubles or contain insoluble components. Additionally, the tablet must not contribute toxic substances to the sewage system, the water supply, or the environment.
The most commonly used disinfectant tablet materials are calcium hypochlorite and trichloroisocyanuric acid. Each of these substances has major drawbacks. Calcium hypochlorite contains insoluble components that can plug the holes in the dispenser, and also contributes to water hardness and scale formation by adding calcium ions to the water. Trichloroisocyanuric acid is a strong acid and can produce objectionable chloramine odors under some circumstances.
A disinfectant tablet that produces an appropriate concentration of disinfectant, with the requisite lifetime and tablet integrity, and without the negative properties discussed above would be an advancement in the art.